1. Field of the Invention
The present invention relates to a construction of a combustion chamber for a spark-ignition engine.
More particularly, it relates to a combustion chamber for an engine provided with a domed auxiliary chamber in the cylinder head thereof.
2. Prior Art
In a spark-ignition engine, in order to suppress the generation of nitrogen oxide and carbon monoxide, the prior engine, for example as disclosed in U.S. Pat. No. 4,433,647 published on Feb. 28, 1984, is so constructed that a domed auxiliary chamber provided with a spark plug is formed in the cylinder head and the auxiliary chamber is connected with a cylinder chamber (a main combustion chamber) by an aperture so as for a turbulent flow of air-fuel mixture to be compressed into the auxiliary chamber at the compression stroke.
However, since the top surface of the piston in the above-mentioned prior art engine with a domed auxiliary chamber is formed flat, the flow of air-fuel mixture compressed into the domed auxiliary chamber is apt to become relatively large swirls. Therefore, the mixing rate of fuel and air can't be enhanced sufficiently.
And on the other hand, in a diesel engine with a swirl chamber, which is formed as a domed cavity in the cylinder head and in which a mouthpiece as a pre-chamber cup is fitted at the entrance thereof to form the swirl chamber, the cylinder head for the diesel engine is intended to be used in common as a cylinder head for a spark-ignition engine by omitting the mouthpiece and making use of the domed cavity as the domed auxiliary chamber for the spark-ignition engine in order to enhance the mass-productivity and reduce the manufacturing cost thereof.
However, in this case, the disposition, the shape, and the capacity of the domed auxiliary chamber for the spark-ignition engine are restricted by the common utilization with the swirl chamber for the diesel engine. Therefore, the mixing condition of fuel and air for the air-fuel mixture gets worse and accordingly the mixing rate thereof also takes a turn for the worse.